Metal-backed nonwelding contact



y 1949- H. L. MEKELBURG 2,468,888

METAL-BACKED NONWELDING CONTACT Filed Sept. 25, 1944 Patented May 3,1949 2,468,888

j UNITED STATES PATENT orrlcs 1 2,468,888. METAL-BACKED NONWELDINGCONTACT Harold L. Mekelburg, Milwaukee, Wis., assignor to Cutler-Hammer,Inc., Milwaukee, Wis., a. corporation of Delaware Application September25, 1944, Serial No. 555,646

10 Claims. 1

This invention relates to improvements in metal-backed non-weldingcontacts, and more particularly to means for protecting the nonweldingsurface portionsthereof from contaminaafford additional advantagesincluding the selfalining or self-centering characteristic of certainearlier forms of contacts.

According to the present invention it is protion by associated. materialemployed to weld or 5 posed to so form the contact and its support asbraze the same to a suitable support. to provide a partially confiningspace or recepta- The invention is especially applicable to and clearound the usual area of attachment between advantageous for that typeof contact which is said parts, to which space the excess of fine silvermolded from powdered materials to provide a or brazing material willfiow when fused and in preform, which preform is heat-sintered and whichsuch excess will be completely or substanthen finally molded under heavypressure to the tially completely accommodated when the welddesiredshape and dimensions. Preferably such ing or brazing operation isperformed. Prefercontact consists of a relatively thick layer of ablythe contact is provided with an integral silver-base material havingnon-welding chardepending skirt or flange to fit over a suitablyacteristics when in use, and a relatively thin formed supporting elementwith sufiicient clearlayer of fine silver integrally united with theance to afford the aforementioned space for the aforementioned layer toenable attachment of excess of fused material, the skirt preferablybethe contact to a metal support of good electrical ing in part (theouter, upper peripheral part) of conductivity by the usual welding orbrazing the same composition as the main body of the operation. Whenbrazing the contact to the supcontact, and at least the inner peripheralsurface port a suitable brazing material is preferably inof such skirthaving such layer of fine silver terposed between the layer offinesilver and the formed integrally therewith. The skirt is prefersupport. In some cases and under certain conably made to fit the supportas closely as it can ditions, however, the brazing material may be beand yet provide the aforementioned spacefor omitted; fusing of the finesilver backing being flowing material, and said skirt is preferablyefiected to provide for uniting or attachment of made as nearlycontinuous as can be convenientthe contact to its support. In the lattercase a ly done. However, it has been found in practice suitable fiux isusually employed merely to prethat complete continuity of the skirt isnot vent oxidation of thetwo metals (fine silver of essential; theembodiment of the inventionherein the backing, and brass or the like ofthe support). illustrated having been highly successful in ac- Suchcontacts are seriously impaired if during complishing the aforestatedobjects. welding or brazing the fine silver of the backing In the priorpatent of Merle R. Swinehart, or the brazing material (which is likewisehighly No. 2,425,053, dated August 5, 1947, (and assigned conducting)flows onto the contact surface or the to the same assignee as thepresent application) peripheral edge of the layer of non-weldingsilver-backed non-welding contacts and methods material affording thecontact surface, and atof making the same are disclosed and broadlytachment of such contacts has heretofore reclaimed. Also in said PatentNo. 2,425,053 there quired great care in order to avoid an excessive isspecifically shown (Figs. 11 to 18) but not number of rejects, ordefective contacts. The claimed a skirted silver-backed non-weldingconfine silver backing must be confined to the back tact of theparticular type herein disclosed and or attaching end of the contact informing the claimed. latter; and both the fine silver backing and theThe accompanying drawings illustrate the. brazing material (if employed)must be so conpreferred form of my invention; it being underfined duringthe attaching operation. Moreover, stood that the invention issusceptible of embodiit i highly important t in re against the edgesment in other forms without departing from the of the contact warping orcurling away from the scope of the appended claims. contact supportthrough inadequate bonding with In the drawings, the latter. Dimculty inthe latter respect has Figure 1 is an enlarged top plan view of a beenexperienced and it has been found that such skirted fine-silver-backednon-welding contact curling of the edges of the contact tends greatlyconstructed or formed in accordance with my to curtail contact life, forobvious reasons. invention, the skirt or depending flange beingOvercoming of the difficulties aforeindicated is shown in dotted lines.a a primary object of the invention; and other I Fig. 2is an endelevation of the contact shown. objects include accomplishment of theforegoing in Fig. 1. 7, object in a way such as. to be economical and toFig. 3 is a side elevational view of said contact;

Fig. 4- is a top plan view of a combined statlonary. metal support andwiring terminal to which the contact of Figs. to 3 is adapted to beattached.

Fig. 5 is a front elevational viewof the metal member shown in Fig. 4.but with the contact secured in position on thesupport by welding orFig.8 is a view similar to Fig. 7, 'but showing the contact attached tothe support.

The fine-silver-backed non-welding contact I is of approximatelyrectangular contour (Fig. 1), and the same has a slightly convex contactface II. Contact I0 is provided with a skirt or depending flange I2forming an extension of one long side and. the two short sides of thecontact, but being omitted at an intermediateportion of the length ofthe other long side thereof, .as indicated at I3 (see Figs. 1, 3 and'7). The, fine silver backing is preferably embodied in the flat innersurface I4 of the contact and the inner surface I5 of the aforementionedskirtI2. Contact I0 is produced in accordance with one or another of themethods disclosed in said Patent No. 2,425,053. That is to say, thelayers of nonwelding contact material I0 and fine silver Ill (Fig. 7)are molded into a unitary preform which is heat-sintered and'then moldedto the final form illustrated under a pressure of approximately 100,000pounds per square inch. It will be noteel'fr'om Fig-7 that'theinnersurface I5 of the skirt or flange I2- has a slightincline outwardlytowards-its lower edge.

Contact I0 is adapted to be rigidly and permanently attached by weldingor brazing to a combined metal support and wiring terminal member I6(Figs. 4 to 6). Thus the fiat inner surface It of contact I0 is adaptedto seat against the upper surface I! 'of the correspondingly shapedportion I8 of the support. The inner surface I5 of flange I2 surroundsthe peripheral edges I8 of portion I8; the portion of flange I2 omittedat I3 being adapted to accommodate the reduced portion or neck of saidsupport at I 9 in Fig. 4. As hereinbefore stated, the skirt or flange I2has clearance from the support to afford space for the excess fusedmaterial, and as will be apparent such space is that bounded by theslightly inclined surface I5 of skirt I2 and the peripheral edges I8 ofportion I8 of the support. In other words, the parts I5 and I8 havingclearance therebetween provide a receptacle I5-I8 In attaching contactII) to portion II! of the support by brazing I prefer to interposebetween the adjacent surfaces of the two parts a thin sheet or plate ofa suitable brazing material or hard solder, as aforementioned.Alternatively a suitable flux may be interposed between the support(formed of brass or the like) and the fine silver backing.

Said neck portion extends laterally at 20 and is formed integrally witha portion extending substantially vertically upward at 2 I; said lateraland vertical portions preferably having a relatively narrow slot 22common thereto to increase the resiliency and flexibility thereof. 'Arectangular terminal portion 23 is formed integrally with verticalportion 2 I, said terminal portion havinga tapped opening 24 therein toaccommodatethe shank of a binding screw 25 (Fig. 6)

As will be understood by those skilled in the art.;theaforementionedflange or skirt l2 of the contact-acts tominim'ize the likelihood offlow of any of thefused'material (fine silver or brazing material) by:capillary action or otherwise,

tothe contact surface II of'contact I0; it being understood 'thatsurface' II will 'befaced up- 1 wardly, during the welding or brazingoperation.

Also the skirt I2 serves to strengthen the contact as a whole and topreventv upward curling or separation thereof from the support portionI8 when in use. The additional engagement or connection afforded by theexcess of fused silver or brazing material 21 (Fig. 8) between the skirtI2 of. contact Ill and the peripheral'edges I8 of portion I8 and thefused silver or brazing material serves to increase the area ofelectrical and mechanical contact between said parts, with v aconsequent increase in the rate of heat dissipar of the contactmay, forexample, consist of a mixture of 82 per cent by weight of Merck'sprecipitated silver powder and 18 per cent by weight of a mixture ofcadmium oxide and cadmium sulphate, wherein 85 per cent of said lastmentioned mixture is cadmium oxide and 15 per cent thereof is cadmiumsulphate. A fine silver backing to have the same proportional degree ofshrinkage as said portion composed of non-welding contact material willpreferably be composed of a mixture of 80 per cent by weight ofprecipitated silver powder and 20 per cent by weight of crystallinesilver powder of non-welding material and a backing therefor of fusiblemetal integrally united therewith, said backing comprising a thin layerof said metal to provide for attachment of the contact to a metalsupport by welding or brazing, and said contact being so shaped as toprovide a receptacle between the same and the metal support for allexcess of fused metal or brazing material, thereby to guard against flowof the fused metal or brazing material onto said active part of thecontact.

2. A molded and heat sintered contact comprising an active part ofsilver-base non-welding material and a backing therefor of fine silverintegrally united therewith. said fine silver being in the form of athin layer to provide for attachment of the contact to a metal supportby welding or brazing, and said contact being so shaped as to provide areceptacle between the same and the metal support for all excess offused silver or brazingmaterial, whereby contamination of the activesurfaces of said' non-welding part by the fused silver or brazingmaterial is avoided.

3. A heat-sintered electrical contact of nonwelding character moldedinto the desired form under heavy pressure from a preformed bodyconsisting of a relatively thick contactface portion composed of silver,cadmium oxide and'cadmium of shrinkage of all portions of said preformedbody during sintering, said back portion of fine silver being adapted toprovide for attachment of said contact to a metal support by welding orbrazing, and said back portion including an integral depending skirt orflange adapted to out the inner surface of said skirt, said bondedvmetal layer providing for attachment of the contact to a metal supportby welding or brazing, and said skirt providing a receptacle for allexcess of fused metal or brazing material, thereby to guard against flowof the fused metal or brazing material onto the operating surface ofsaid non-welding material.

5. A pressure molded and heat-sintercd contact comprising an upperactive part of silverbase non-welding contact material and a lower orbacking part consisting of a thin layer of fine silver, said contacthaving a downwardly extending marginal skirt formed integrally with saidactive part and said fine silver layer whereby the latter extendsthroughout the inner surface of said skirt, saidflne silver layerproviding for attachrnent of the contact to a suitably shaped metalsupport by welding or brazing, and said skirt providing between the sameand the metal support a receptacle for all excess of fused silver orbrazing material to insure against flow of the latter onto the exposedor operating surfaces of said non-welding material.

6. A pressure molded and heat-sintered contact comprising anupper activepart of silverbase non-welding contact material and a lower or backingpart consisting of a thin layer of fine silver, said contact having adownwardly extending marginal skirt formed integrally with said activepart and said fine silver layer whereby the latter extends throughoutthe inner surface of said skirt, said fine silver layer providing forattachment of the contact to a suitably shaped metal support by weldingor brazing, said skirt providing between the same and the metal supporta receptacle for all excess of fused silver or brazing material toinsure against flow of the latter onto the exposed or operating surfacesof said non-welding material, and said fused silver or brazing materialcooperating with said skirt and said support to improve the electricaland mechanical connection between the latter and said contact.

7. A non-welding contact molded from powdered material with a backing offusible metal, said backing comprising a thin layer of metal to be fusedfor attachment of the contact to a metal support, and said contactincluding an integral skirt at the margin thereof for stiffening of thecontact and to provide a receptacle for all excess of the fused metal,thereby to guard against now of the fused metal onto the non-weldingportion of the contact. Y

8. A heat-sintered electrical contact molded under heavy pressure frompowdered materials, said contact comprising an active part consisting ofa silver-base non-welding material and a backing of fine silver, saidbacking providing for attachment of the contact to a metal support bywelding or brazing, and said contact including an integral skirt at itsmargin for stiffening or reinforcing the same and to accommodate anyexcess of the fused silver or brazing material, thereby to substantiallyprevent fiow of the fused silver or brazing material to the non-weldingportion of said contact.

9. The combination with a metal contact support, of a contact comprisinga non-welding body having bonded thereto a thin layer of fusible metal,said contact being attached to said support by fusion of said fusiblemetal, a marginal skirt formed integrally with said contact, at leastthe inner periphery of said skirt being composed of said fusible metal,and said skirt fitting onto a part of said support with sufllcientclearance to sintered contact molded under heavy pressure from powderedmaterials and comprising a nonwelding body having bonded thereto by themolding operation a thin layer of fine silver, said contact beingattached to said support by welding or brazing through the medium ofsaid layer of fine silver, said contact having an integral marginalskirt the outer peripheral surface of which is composed mainly of saidnon-welding material and the inner peripheral surface of which iscomposed of the fine silver of said layer, and said skirt fitting onto apart of said support with sufllcient clearance to afford space for allexcess of fused silver or brazing material, to thereby substantiallycompletely insure against flow of the fused silver or brazing materialonto said body of non-welding material. HAROLD L. MEKELBURG.

REFERENCES CITED The following references are of record in the file ofthis patent:

